1. Field of the Invention
The invention relates to a filament lamp with bases. In particular, the invention relates especially to a filament lamp with bases in which, in a pinch seal area, a base composed of a ceramic is attached to each of two ends of a tubular bulb without using an adhesive.
2. Description of Related Art
Filament lamps with bases are known in which no adhesive is used at locations at which an outer lead extends from an end of the lamp and a feed line from a power source or the like are welded to one another. This lamp has an arrangement in which, in a plate-shaped terminal, the respective outer lead which projects out of the respective pinch seal area on the two ends of the tubular bulb is welded to the tip of the feed line and these weld points are protected by ceramic bases.
FIGS. 6 and 7 schematically show one such filament lamp with bases. FIG. 6 shows a perspective view of only one end of a filament lamp with bases. FIG. 7 shows a cross section of the end of the filament lamp with bases as shown in FIG. 6, the lamp being viewed from the direction of a through opening 92 which is located in a base 70. The lamp has a bulb 1, with a flattened pinch seal area 2 which is located on each of two ends of the bulb 1, a molybdenum foil 3, a filament 4, a supporter 5 for holding the filament, an outer lead 6 with one end connected to the molybdenum foil 3 and its other end extending from the pinch seal area 2, and a ceramic base 70.
As is shown in FIG. 7, the base 70 has a concave holding part 71 on one end to hold the pinch seal area 2. The outer lead 6 which extends from the pinch seal area 2 is inserted into a first opening 90 which is located in the bottom of the holding part 71. On the other end of the base 70, a second opening 91 is formed into which a feed line 81 is inserted which is connected to a power source or the like. A plate-shaped terminal 8 is attached to the tip of this feed line 81. This terminal 8 and the outer lead 6 are electrically connected to one another by welding.
Between the first opening 90 and the second opening 91, a through opening 92 is formed in the direction which orthogonally intersects the lengthwise direction of the base 70 and a welding rod (not shown) is inserted into the through opening from its two ends. Thus, the location at which the terminal 8 and the outer lead 6 are in contact with one another is welded. As a result, in the pinch seal area 2, an electrical connection is enabled without using adhesive.
In one such conventional filament lamp with bases, however, there was the following disadvantage:
The direction of the pinch seal area 2 which is held in the holding part 71 of the base 70 and the direction of the plate-shaped terminal 8 are hardly considered. If, in the direction in which the wider crimped foot surface 2A of the pinch seal area 2 and a flat plane 8A of the plate-shaped terminal 8 intersect orthogonally, welding is performed, a stress is applied to the terminal 8 in the directions of the arrows shown in FIG. 7 and this stress is transferred to the outer lead 6; this leads to fracturing of the pinch seal area 2.
The plate-shaped terminal 8 can absorb stress by bending when the stress is applied from a direction which orthogonally intersects the plane 8A. However, the terminal 8 cannot absorb stress when the stress is applied from a direction parallel to the plane 8A (i.e., in the directions of the arrows shown in FIG. 7). This stress is transferred directly to the outer lead 6. Since the pinch seal area 2 has a flattened shape and is weak against stress in the direction which orthogonally intersects the wider crimped foot surface 2A, it is therefore damaged by the stress transferred to the outer lead 6.
If, between the holding part 71 of the base 70 and the pinch seal area 2, there is a large gap, the pinch seal area 2 is tilted within the holding part 71. If it is extremely tilted, the peripheral edge area A of the first opening 90 of the base 70 borders the outer lead 6. This border point functions as an articulation point and the outer lead 6 is exposed to a stress. When this stress is exerted in a direction which orthogonally intersects the wider crimped foot surface 2A of the pinch seal area 2, for the above described reason, there is the disadvantage that the pinch seal area 2 is damaged.
The invention was devised to eliminate the above described disadvantage in the prior art. Therefore, a primary object of the invention is to devise a filament lamp with bases in which the pinch seal areas are not damaged and no adhesive is used.
The above object is achieved in accordance with the invention in a filament lamp with bases which comprises:
a tubular bulb with a flattened pinch seal area formed on each of its two ends;
a filament which is located within the bulb along the longitudinal axis;
outer leads which are electrically connected to the filaments and which project out of the pinch seal area; and
bases of ceramic for protection of the plate-shaped terminals which electrically connect the outer leads to the feed lines, by
the respective ceramic base on one side being provided with a concave holding part for holding of the pinch seal area and a first opening into which the outer lead which is located in the holding part is inserted, and the respective base on the other side has a second opening into which the plate-shaped terminal is inserted,
an opening being provided between the first opening and the second opening which is used to weld the outer lead and the plate-shaped terminal to one another in a direction which orthogonally intersects the lengthwise direction of the base and orthogonally intersects the wider crimped foot surface of the pinch seal area in the holding part,
the respective plate-shaped terminal being larger than the first opening of the base and being welded to the outer terminal such that its flat plane is parallel to the wider crimped foot surface of the pinch seal area.
Furthermore, the object is achieved according to the invention by the holding part of the respective base essentially having the same shape as that of the accommodated pinch seal area, and the distance between the side of the pinch seal area from which the outer lead does not project and the inside of the holding part which is opposite this side is smaller than the distance between the outer lead which penetrates the first opening of the base and the peripheral edge area of this opening.
In the following, the invention is specifically described using an embodiment shown in the drawings.